This paper presents the results of a study on the effect of geopolymer coating on mild steel. Geopolymer is synthesis of a fly ash and alkaline activators which are sodium hydroxide solution (NaOH) and sodium silicate solution (Na₂SiO₃). Fly ash is one of residue produced during the combustion of coal in coal power plant. In this study, fly ash class F based geopolymer was used as a source material. The alkaline activators then were mixed with fly ash to produce the geopolymer paste which acts as a coating material. The mixture was placed in molds and reinforcement bar were embedded in geopolymer paste. After that, the corrosion behavior of reinforcement bars for all samples were observed by using Open Circuit Potential (OCP) testing. Referring the pourbaix diagram regarding OCP testing, samples are in passivity region. Besides that, mild steel also were coated with geopolymer paste for adhesion test. Elcometer 108 was used for adhesion strength test. Morphology analysis also been used to determine the microstructure of fly ash and geopolymer paste. Phase analysis was used for the analysis phase between fly ash, geopolymer paste and mild steel coated with geopolymer paste. From OCP test, pourbaix diagram shows that samples is placed in the passivity region, iron (III) oxide (Fe₂O₃) which is in stable phase and iron (II, III) oxide same results as in phase analysis. The minimum potential value for OCP is 0.015 V and the maximum potential value is 0.133 V. For adhesion strength, day 14 got the highest results compared day 7 and day 3 which the results are 2.0 Mpa, 1.9 Mpa and 1.5 Mpa respectively. It is because from day 3 until day 14, the structure of geopolymer paste becomes more compact, denser and better crystallization as shown in morphological analysis.

To fabricate a lead-free solder with better properties, a surface-modified precipitate calcium carbonate (PCC) was added as a reinforcement phase to tin-zinc (Sn-9Zn) solder. The surface modification of PCC was done by using electroless plating to deposit nickel (Ni) layer on the PCC. Based on microstructure analysis, a thin layer of Ni was detected on the reinforcement particle, indicating the Ni-coated PCC was successfully formed. Next, composite solder of Sn-9Zn-xNi-coated PCC (x = 0, 0.25, 0.50, 1.00 wt.%) was prepared. The morphology and phase changes of the composite solder were evaluated by using optical microscope and X-ray diffraction (XRD). Significant refinement on the grain size of Zn was seen with the additions of Ni-coated PCC, with a new phase of Ni3Sn4 was detected along with the phases of Sn and Zn. The wettability of Sn-9Zn was also improved with the presence of Ni-coated PCC, where the wetting angle decreased from 28.3° to 19.4-23.2°. Brinell hardness test revealed up to 27.9% increase in hardness for the composite solder than the pristine Sn-9Zn solder. This phenomenon contributed by the increased in dislocation resistance through Zener pinning effect and Zn grain refinement within the composite solder which enhanced the overall properties of the composite solder.

This paper aims to find out the effect of different weight percentages of geopolymer filler in glass-reinforced epoxy pipe, and which can achieve the best mechanical properties and adhesion between high calcium pozzolanic-based geopolymer matrices. Different weight percentages and molarities of epoxy hardener resin and high calcium pozzolanic-based geopolymer were injected into the glass fiber. By manually winding filaments, composite samples were produced, and they were then allowed to cure at room temperature. To determine how well the geopolymer matrices adhere to the fiber reinforcement, the microstructure of the composites’ surfaces and perpendicular sections were examined. Maximum values of compressive strength and compressive modulus were 94.64 MPa and 2373.58 MPa, respectively, for the sample with a weight percentage of filler loading of 30 wt% for an alkali concentration of 12 M. This is a relatively wide range of geopolymer weight percentage of filler loading from 10 wt% to 40 wt%, at which we can obtain high compressive properties. By referring to microstructural analysis, adhesion, and interaction of the geopolymer matrix to glass fiber, it shows that the filler is well-dispersed and embedded at the fiber glass, and it was difficult to determine the differences within the range of optimal geopolymer filler content. By determining the optimum weight percent of 30 wt% of geopolymer filler and microstructural analysis, the maximum parameter has been achieved via analysis of high calcium pozzolanic-based geopolymer filler. Fire or elevated temperature represents one of the extreme ambient conditions that any structure may be exposed to during its service life. The heat resistance or thermal analysis between glass-reinforced epoxy (GRE) pipe and glass-reinforced epoxy pipe filled with high calcium pozzolanic-based geopolymer filler was studied by investigating burning tests on the samples, which shows that the addition of high calcium pozzolanic-based geopolymer filler results in a significant reduction of the melted epoxy.

This research analyzes the effect of sodium hydroxide (NaOH) solution concentration ranging from 8M to 12M as alkaline activator on the properties of geopolymer paste. Alkaline activator is essentially a mixture of sodium hydroxide and sodium silicate solution. In this research, the main component used was raw kaolin. In order to produce kaolin based geopolymer paste, the alkaline activator solution was prepared with 0.24:1.00 ratio of Na₂SiO₃/NaOH and this alkaline activator solution was prepared for 24 hours prior before used in another process. The solid-to-liquid ratio which is kaolin-to alkaline activator solution ratio was 0.80:1.00. The mixture of kaolin based geopolymer paste were placed in cube moulds with a size of 50x50x50 mm, and left for 24 hours until it hardened. Then, the samples were cured at 80? in the oven for 24 hours. The samples of kaolin based geopolymer paste were tested based on compressive strength, morphology analysis, water absorption and porosity after 28 days. In this project, 8M concentration of NaOH solution was the best concentration in order to study the synthesis of kaolin based geopolymer paste as the sample had the highest amount of compressive strength with 0.992 MPa and had the lowest water absorption and porosity with 1.246% and 24.08% respectively. Scanning Electron Microscope (SEM) was used to observe the morphological structure of the kaolin based geopolymer paste. The sample with 8M concentration of NaOH solution shows that least amount of unreacted particles. The structure of kaolin based geopolymer paste was more dense at 8M concentration as the size of pore decreases. The kaolin based geopolymer paste is suitable for use in the construction building industry as a finishing product such as coating.

This project studies the influence of different grain sizes of Ni-based Fe-33Ni-19Cr alloy obtained from heat treatment procedure on high temperature isothermal oxidation. Heat treatment procedure was carried out at two different temperatures, namely 1000℃ and 1200℃ for 3 hours of soaking time, followed by quenching in the water. These samples are denoted as T1000 and T1200. The heat-treated Ni-based Fe-33Ni-19Cr alloy was subjected to an isothermal oxidation test at 950℃ for 150 hours exposure. Oxidized heat-treated alloys were tested in terms of oxidation kinetics, phase analysis and surface morphology of oxidized samples. Oxidation kinetics were determine based on weight change per surface area as a function of exposure time. Phase analysis was determined using the x-ray diffraction (XRD) technique and surface morphology of oxidized samples was characterized using a scanning electron microscope (SEM). As a result, the heat treatment procedure shows varying grain sizes. The higher the heat treatment temperature, shows an increase in grain size with a decrease in hardness value. The oxidation kinetics for both heat-treated samples showed an increment pattern of weight change and followed a parabolic rate law. The oxidized T1000 sample recorded the lowest parabolic rate constant of 3.12×10–8 mg2cm–4s–1, indicating a low oxidation rate, thus having good oxidation resistance. Phase analysis from the XRD technique recorded several oxide phases consisting of Cr2O3, MnCr2O4, and (Ti0.97Cr0.03)O2 oxide phases. In addition, a uniform oxide layer is formed on the oxidized T1000 sample, indicating good oxide scale adhesion, thereby improving the protective oxide behavior.